It looks more like the typical difficulty with 3D transparency, sorting, depth buffer and render order. It is not yet easy to solve in C3 (or 3D engines in general!)
Viewing post in Construct 3 3DObject Plugin comments
Yes. I think too... this is C3 trouble...
You great man. Best regards!!!
Have you considered point light sources (no LightLayer3D) and working with shadows.
I remember the Q3D (banned by Scirra) on the C2. Point light sources worked very correctly there. You had to place them as a 3D model, adjusting the height... but they worked...
I can find
https://www.construct.net/en/free-online-games/animacion-reflejos-3d-30795/play
Thanks for the comments.
Point light sources need more information exposed in the C3 effect SDK, I have requested this, but no response yet.
In general 3DObject is not a full scene 3D addon, it is focused only on the model itself/object itself. I would classify Q3D/three.js/babylon.js as more scene based engines.